Quantitative assay of copper, iron, nickel, and zinc in fuel ethanol samples by flame atomic absorption spectrometry - Oliveira, Marcelo Firmino de; Balbo, Valdir Roberto; Andrade, José Fernando de; Saczk, Adelir Aparecida; Okumura, Leonardo Luiz; Stradiotto, Nelson Ramos (Chemistry and Technology of Fuels and Oils, 2008)